Most Potent Greenhouse Gases Revealed

Greenhouse gases containing fluorine molecules are among the
worst environmental offenders because they trap heat in the Earth’s atmosphere
most efficiently, according to a new NASA study.

For the study, NASA scientists analyzed dozens of compounds
and ranked greenhouse gases as global warming agents to
create guidelines for minimizing global warming. The goal is for chemical
companies to use NASA’s guidelines during the creation of potent greenhouse
gases such as perfluorocarbons (PFC) and hydrofluorocarbons (HFC), which are
used in everyday items such as air
conditioners.

The study, detailed in the May 3 issue of the journal
Proceedings of the National Academy of Sciences, found that several chemicals
that contained fluorine were stronger greenhouse gases than those containing
chlorine or hydrogen, including PFCs, HFCs and chlorofluorcarbons (CFCs), which
were implicated in the destruction of the ozone layer.

The researchers in particular looked at how the number and
placement of fluorine atoms within a chemical molecule affected the potency of
that chemical as a greenhouse
gas.

“Once we discovered the molecular properties that cause
molecules to absorb radiated heat more efficiently, we were able to design
strategies that will minimize the global warming contribution of materials,”
said study co-author Timothy Lee, the chief of the Space Science and
Astrobiology Division at NASA’s Ames Research Center in Moffett Field, Calif.

Lee and colleagues looked at five classes of fluorinated
compounds because they are highly efficient at trapping heat. The researchers
ranked the chemicals by their heat-trapping efficiency, known as a molecule’s
radiative efficiency, to determine which chemicals were more harmful.

Simply reducing the number of fluorine atoms isn’t enough to
reduce a chemical’s environmental impact. The study makes specific
recommendation about the orientation and number of fluorine molecules within
greenhouse gases. However, the study did not take into account the toxicity,
atmospheric lifetime (how long a chemical stays in the air), or the atmospheric
fate of these fluorinated compounds.

A longer carbon chain was also linked to more efficient
heat-trapping in some compounds.

Screening for a chemical’s radiative efficiency is one
additional constraint that greenhouse gas manufacturing companies could use in
their design process, the study’s authors said.

Brett Israel

Brett Israel was a staff writer for Live Science with a focus on environmental issues. He holds a bachelor’s degree in biochemistry and molecular biology from The University of Georgia, a master’s degree in journalism from New York University, and has studied doctorate-level biochemistry at Emory University.